Spark ignition apparatus



Patented Jan. 6, 1970 3,488,514 SPARK IGNITION APPARATUS John E. Lundberg, Richfield, Minn., assignor to Honeywell Inc., Minneapolis, Minn., a corporation of Delaware Filed June 19, 1968, Ser. No. 738,298 Int. Cl. H01h 47/32 U.S. Cl. 307-117 6 Claims ABSTRACT OF THE DISCLOSURE Background of the invention The present invention has particular utility in the burner control art where it is desirable to ignite a fuel by means of a spark. This has been accomplished in the past by the use of bulky transformers which provide the necessary high voltage spark between spark electrodes. It has also been known to use a silicon controlled rectifier to discharge a capacitor through a relatively small transformer and this last arrangement is successful with light fuels such as gas. The use of silicon controlled rectifiers and charged capacitors is more limited in capacity than simple step-up transformer arrangements that are much larger, and attempting to avoid this limitation has led to the present invention. The present invention allows for more energy to be transferred from the capacitor to the generated spark thereby making the device more reliable and useable on heavier fuels than would otherwise be ignitable by this type of an arrangement.

Summary of the invention The present invention is a means of obtaining a higher transfer of energy through a spark ignition transformer from a charged capacitor to the spark electodes. The arrangement utilized in the present invention charges the capacitor through a conventional diode arrangement for subsequent discharge by a silicon controlled rectifier. When the discharge of the stored energy is accomplished through the primary winding of a spark ignition transformer and silicon controlled rectifier, the applied line voltage is still of such a polarity as to be capable of supplying more energy to the primary of the transformer. This is possible since the spark discharge occurs in a much shorter period of time than one half of a cycle of the applied normal alternating current. This is taken advantage of by placing a charging diode across the silicon controlled rectifiers so that the charging path for the capacitor passes through the primary winding of the spark ignition transformer thereby supplying an additional pulse of energy through the transformer in recharging the capacitor. This additional pulse of energy is transferred to the spark during the half-cycle when the spark is active from the original discharge of the storage capacitor.

Brief decription of the drawing The single schematic circuit in the drawing is an actual spark ingnition circuit as controlled by a flame responsive safety type device.

Description of the preferred embodiment The ignition apparatus of the present invention is generally disclosed at 10 operating in conjunction with a primary control generally disclosed at 11. The primary control 11 is of a type disclosed in the US. Patent 3,380,- 796 to Arlon D. Kompelien which issued on Apr. 30, 1968. It will be briefly described in conjunction with the ignition apparatus 10.

The ignition apparatus 10 has a pair of terminals 12 and 13 that are adapted to be connected to a source of alternating current 14. The alternating current source 14 is a conventional volt, 60 cycle source. A third terminal 15 is provided for connection of the ignition apparatus to a burner 16 by means of conductors 17 and 18. The burner 16 can be any type but most easily can be considered a burner for utilization of gas by means of the operation of a solenoid gas valve. The burner 16 also cooperates with an ignition responsive means 20 that has been disclosed as connected to a pair of terminals 21 and 22 for the primary control 11. The ignition responsive means 20, in the present disclosure, is a photoresponsive cell that changes resistance with exposure to flame, as is well-known in the art and specifically described in the previously mentioned issued Kompelien patent.

The burner 16 also cooperates with a pair of spark electrodes 23 and 24 across which a spark is to be generated to ignite the fuel issuing in the burner 16 in a conventional fashion. The electrode 24 is connected to ground 25 for potection in the system and is further connected to a transformer step-up winding 26 in which a high voltage ignition potential is generated. The transformer winding 26 is associated with an ignition transformer disclosed as 27 which has a primary winding 28. The primary winding 28 is connected between a controlled rectifier 30 and a capacitor 31. The controlled rectifier 30 is disclosed as a silicon controlled rectifier having an anode 32, a cathode 33, and a gate or control electrode 34. The capacitor 31, in addition to being connected to the transformer primary 28 is connected by conductor 35 to a normally open relay contact 36 and a further conductor 37 to terminal 15. The normally open contact 36 is also connected by a conductor 38 to terminal 13 of the alternating current supply. It is obvious that when the contact 36 closes, power is applied from conductor 38 to conductors 35 and 37 to energize the burner 16 and to supply energy to the capacitor 31.

A diode 40 having an anode 41 and a cathode 42 is connected across the controlled rectifier 30. The cathode 42 of the diode 40 is connected to the anode 32 of the silicon controlled rectifier 30 while the anode 41 of the diode 40 is connected to the cathode 33 of the silicon controlled rectifier 30. A conductor 43 joins the common connection of the anode 41 and cathode 33 to a further conductor 44 that connects to a conductor 45 which in turn is connected to terminal 12 of the alternating current supply 14. The conductors 38 and 45 supply power to a primary winding 46 of a step-down transformer 50 that has a tapped secondary winding 51 to supply power to the primary control 11.

Connected between the control electrode or gate 34 of the silicon controlled rectifier 30 and the conductor 43 is a resistor 52 across which a signal is generated for operation of the silicon controlled rectifier. Also connected across the resistor 52 is a circuit including resistor 53 and a secondary winding 54 of a transformer 55. Transformer 55 is a small pulse type of transformer that saturates quite rapidly when voltage is applied to a primary winding 56 of the transformer. The pulse transformer 55, when energized, provides an initial pulse of voltage to the silicon controlled rectifier 30 to cause it to conduct. The pulse is 3 shorter in duration than one-half of the applied voltage cycle of the source 14.

Connected to the primary winding 56 is a relay 60 which has the previously mentioned normally open contact 36 as one of its contacts. Also associated with relay 60 is a normally open contact 61 that operates in conjunction with the contact 36. The relay 60 is connected between the primary winding 56 of the transformer 55 and a terminal 62 that in turn is connected through a thermostat or control means 63 (disclosed as a bimetal operated switch) to a terminal 64. The terminal 64 is connected through a normally closed safety switch contact 65 to the center-tapped winding 51 of transformer 50. The normally closed safety switch contact 65 is mechanically operated by linkage 66 from a heater resistor 67 that forms part of a conventional resistance heating type of safety switch that is Well-known in the art.

The relay 60 is also connected by conductor 70 to the normally open contact 61 and the contact 61 is further connected by conductor 71 to a center-tap 72 in the secondary or step-down winding 51 of transformer 50. A silicon controlled rectifier 73 is connected in series with the primary winding 56 of the pulse transformer 55 and through a conductor 74 to the safety switch heater 67. Also connected to conductor 74 is a resistor 75 which completes a back-bias circuit for the silicon controlled rectifier 73.

Connected from the terminal 62 is a voltage divider and stabilization network made up of conductor 80, resistors 81, 82, 83, and potentiometer 84 to a conductor 85 that is connected to the step-down winding 51 of the transformer 50. A Zener diode 86 for stabilizing part of the voltage is connected between the junction of the resistors 81 and S2 and the conductor 85. The reason for this Zener diode and the resistance network made up of resistors 81, 82, 83, and the potentiometer 84 was the basis of the previously mentioned invention in the Kompelien Patent 3,380,796. Completing the circuit for the primary device is a capacitor 90 for suppression of transients between the gate and cathode of the silicon controlled rectifier 73. The pair of terminals 21 and 22 connect an input signal from the ignition responsive means 20 across resistor 83 and potentiometer 84. Since the proper phasing of the applied alternating current voltage is quite important to the present invention, the transformers 50 and 55 have been disclosed with polarity dots to indicate the winding polarity of the primary and secondary windings. The dots represent the same polarity in existence at a particular instance of time.

Operation The circuit as disclosed is in a standby condition with the thermostat 63 open and the relay 60 de-energized. With relay 60 de-energized contacts 36 and 61 are open and the igniter apparatus is de-energized. Upon a need for heat, the thermostat 63 closes thereby supplying electrical power to a series circuit made up of the relay 60, the pulse transformer primary winding 56, the silicon controlled rectifier 73 and the safety switch heater resistance 67. The circuit is completed by conductor 85 to the transformer secondary 51 and through the safety switch 65 back to the thermostat 63. This energizing circuit causing the silicon controlled rectifier 73 to conduct as a positive potential occurs at conductor 80 with respect to conductor 85. Conduction occurs due to the bias network, as explained in the Patent 3,380,796 which describes the step-down control 11 in detail. The gate of silicon controlled rectifier 73 has adequate voltage applied at this same time to cause the silicon controlled rectifier 73 to conduct each positive half cycle thus applied between the conductors 80 and 85 whenever the ignition responsive means or photocell is exposed to a dark or fiameless atmosphere. Since no flame exists at the present time in the mode of operation, the conduction occurs through the silicon controlled rectifier 73.

This conduction energizes the relay 60 and causes the contacts 61 and 36 to close. The closing of contact 61 completes a holding circuit for the relay 60 from the center-tap 72 through conductors 71 and 70. At the same time, a voltage is supplied through the contact 36 from terminal 13 to the burner 16 to supply fuel, such as gas to the location of the spark electrodes 23 and 24. If a spark is now generated, which will occur in the present ignition apparatus 10, the burner 16 will light.

In the spark ignition apparatus 10, the closing of contact 36 applies voltage from terminals 12 and 13 through conductors 44 and 45 to the anode 41 of the diode 40 and through the primary Winding 28 of transformer 27 to the positive marked side of the capacitor 31. This charging path occurs on the first positive half cycle of the applied alternating current voltage but does not cause and sparking, as it merely provides a charging path for the capacitor 31. The negative applied first half cycle has no effect on the circuit and the circuit is now ready to cause ignition upon the next positive half cycle. Upon the application of the second positive half cycle, and the subsequent positive half cycles, the ignition apparatus 10 is ready to generate a high intensity spark between electrodes 23 and 24. When the next positive half cycle is applied current is drawn through the primary winding 56 of the pulse transformer 55 and through the silicon controlled rectifier 73. As was previously noted, the pulse transformer 55 provides a voltage in the secondary winding 54 with its positive potential connected through resistor 53 to the gate 34 of the silicon controlled rectifier 30. The pulse of energy in the secondary winding 54 is quite short in duration since the transformer 55 is a saturating type of transformer. This short pulse of energy at the gate 34 of the silicon controlled rectifier 30 causes it to go into conduction since the capacitor 31 has a charge as noted in the drawing. The capacitor 31 discharges through the primary winding 28 of the spark ignition transformer 27 and through the silicon controlled rectifier 30 by way of the anode to cathode circuit. The discharge circuit is completed through conductor 43 back to the line terminal 12 of the alternating current supply 14 and through the source 14 back to the terminal 13, conductor 38, contact 36, and conductor 35. It has been found that the alternating current supply 14 has an impedance of about 1 ohm and therefore the discharge path for the capacitor, in passing through the source 14 finds a relatively low impedance. The discharge of the capacitor 31 occurs in a very short period of time thereby generating an ignition spark between electrodes 23 and 24.

The discharge occurs in a fraction of the applied alternating current cycle and lowers the back-bias potential on the diode 40 sufficiently so that a conduction path occurs once again during the same positive half cycle from the terminal 12 through the diode 40, the primary winding 28, and into the capacitor 31. That is, the capacitor 31 is discharged through the primary winding 28 by the silicon controlled rectifier 30 and is again recharged through the diode 40 and the winding 28 prior to the end of the applied positive half of the cycle during which the spark is initiated. With this arrangement, the spark ignition transformer 27 has two flows of energy in its primary winding 28 which generate an initial spark across electrodes 23 and 24, and maintain this spark since once it has been established it is easier to maintain than to initially establish. The flow of energy out of capacitor 31 is supplemented by the flow of energy back into capacitor 31 in the same half cycle of the applied line voltage thereby supplying more energy through the transformer 27 then would be available solely by discharging the capacitor 31. This charging and discharging function of the capacitor 31 can only be accomplished if the triggering signal to the gate 34 of the silicon controlled rectifier 30 is available for a short portion of the early part of the applied alternating current signal. The triggering pulse can turn the silicon controlled rectifier 30 on and then be removed so that the diode 40 can again become forward biased to conduct and recharge the capacitor 31 during the same half cycle. On the negative or alternate half cycle, the present circuit has no active function but merely waits for the next positive applied line cycle.

As soon as a sufiicient spark has been applied between the electrodes 23 and 24 to ignite the fuel at burner 16, the photocell 20 senses the existence of the flame and changes its impedance to remove the bias from the gate of the silicon controlled rectifier 73 thereby removing it from conduction. When the silicon controlled rectifier 73 ceases to conduct, the pulse transformer 55 becomes inactive thereby de-energizing the spark ignition apparatus and stopping the flow of energy through the spark ignition transformer 27. It is noted that the relay 60 remains energized through contact 61 and conductors 70 and 71 to the center-tap 72 of transformer 50 until the thermostat 63 opens circuits to drop the relay out.

Actual measurements of the energy flow through the spark ignition transformer 27 have disclosed that not only is more energy available through the expedient of charging and discharging the capacitor 31 through the primary 28 during a positive half cycle applied to the system then would be available by merely discharging the capacitor, but another phenomenon occurs adding to the energy level of the spark. Due to the inductive reactance of the primary winding 28, a potential is generated across the capacitor 31 that is larger in magnitude than the peak line voltage applied and which would ordinarily be expected. It has been found that a capacitor which would normally .be expected to charge to a voltage of about 170 volts from an ordinary 115 volt alternating current supply actually charges to well over 200 volts due to the inductive efiect that is supplied by the arrangement disclosed. This additional benefit supplies a hotter spark with more energy than would be available in conventional spark ignition apparatus.

The present ignition apparatus 10 has been disclosed as being operated in conjunction with a specific primary control 11 utilizing a pulse transformer 55 to generate the triggering signal for the controlled rectifier. This is merely one of many ways that the electrical control means for the spark ignition apparatus could generate a pulse for rendering the control rectifier conductive during only a portion of one half cycle of the applied alternating current in which the associated diode is fonward biased. Since the present circuit can be modified in many ways without departing from the scope of the present invention, the applicant wishes to be limited in the scope of his invention solely by the scope of the appended claims.

The embodiments of the invention in which an exclusive property or right is claimed are defined as follows:

1. Ignition apparatus including a pair of terminals adapted to be connected to a source of alternating current, comprising: a capacitor; a step-up transformer ineluding a primary winding and having a secondary winding; a diode having an anode and a cathode; first circuit means connecting said diode, said primary winding, and said capacitor in a series circuit to said pair of terminals; a. controlled rectifier having an anode, a cathode and a control electrode; second circuit means connecting the anode of said control rectifier to the cathode of said diode and further connecting the cathode of said controlled rectifier to the anode of said diode; and electrical means having an input connected to said pair of terminals to be energized from the source of alternating current, and including an output connected to the control electrode of said control rectifier; said electrical means being constructed and arranged to render said controlled rectifier conductive only during a portion of the half cycles of the source of alternating current during which said diode is forward biased by the source of alternating current.

2. An ignition apparatus as described in claim 1 wherein said electrical means includes transformer means having an output winding included in said electrical means output and which winding is connected to said control electrode.

3. An ignition apparatus as described in claim 2 wherein said transformer means is a saturable transformer including said output winding to render said control rectifier conductive before saturation occurs in said saturable transformer.

4. An ignition apparatus as described in claim 3 wherein said electrical means further includes ignition responsive means to de-energize said control electrode upon said ignition responsive means sensing a flame.

5. An ignition apparatus as described in claim 1 wherein said controlled rectifier is a silicon controlled rectifier and said control electrode is a gate electrode.

6. An ignition apparatus as described in claim 1 wherein said electrical means includes ignition responsive means to de-energize said control electrode upon said ignition responsive means sensing a flame.

References Cited UNITED STATES PATENTS 3,318,358 5/1967 Potts 43169 3,338,288 8/1967 Walker 431-69 3,380,796 4/1968 Kompelien 431-68 3,393,039 7/1968 Eldridge et a1. 431-74 XR FREDERICK L. MATTESON, JR., Primary Examiner ROBERT A. DUA, Assistant Examiner 

